Synthesis and evaluation of the effect of structural parameters on recovery rate of shape memory polyurethane-POSS nanocomposites

POSS and SSQ Materials in Dental Applications: Recent Advances and Future Outlooks

Recently, silsesquioxanes (SSQ) and polyhedral oligomeric silsesquioxanes (POSS) have gained much interest in the area of biomaterials, mainly due to their intrinsic properties such as biocompatibility, complete non-toxicity, the ability to self-assemble and to form a porous structure, facilitating cell proliferation, creating a superhydrophobic surface, osteoinductivity, and ability to bind hydroxyapatite. All the above has resulted in new developments in medicine. However, the application of POSS-containing materials in dentistry is still at initial stage and deserves a systematic description to ensure future development. Significant problems, such as reduction of polymerization shrinkage, water absorption, hydrolysis rate, poor adhesion and strength, unsatisfactory biocompatibility, and corrosion resistance of dental alloys, can be addressed by the design of multifunctional POSS-containing materials. Because of the presence of silsesquioxanes, it is possible to obtain smart materials that allow the stimulation of phosphates deposition and repairing of micro-cracks in dental fillings. Hybrid composites result in materials exhibiting shape memory, as well as antibacterial, self-cleaning, and self-healing properties. Moreover, introducing POSS into polymer matrix allows for materials for bone reconstruction, and wound healing. This review covers the recent developments in the field of POSS application in dental materials and gives the future perspectives within a promising field of biomedical material science and chemical engineering.

THE STUDY OF INTERMOLECULAR INTERACTIONS IN THE POSS-CONTAINING NANOCOMPOSITES BASED ON POLYURETHANE AND POLYURETHANE/POLY(HYDROXYPROPYL METHACRYLATE) MATRICES

The nanocomposites based on polyurethane matrix and multicomponent polymer matrices consisting of polyurethane and poly(hydroxypropyl methacrylate) with different contents of the last, and 1,2-propanediolisobutyl polyhedral oligomeric silsesquioxane (1,2-propanediolisobutyl-POSS), which was used as a functionalized nanofiller, were synthesized. The influence of the content of 1,2-propanediolisobutyl-POSS on intermolecular interactions and structural features of the nanocomposites was investigated by the method of IR-spectroscopy with Fourier transformation and attenuated total reflection (FTIR-ATR). The study of thermal curing of the model system, which consists of the adduct of trimethylolpropane with toluene diisocyanate and 1,2-propanediolisobutyl-POSS, made it possible to conclude that 1,2-propanediolisobutyl-POSS participates in the reaction of urethane formation using of one of the terminal hydroxyl groups, and it is incorporated into the polymer chain between cross-linking of polyurethane networks. The investigation of multicomponent polymer matrices by FTIR-ATR spectroscopy was done and was shown that photopolymerization of second polymer poly(hydroxypropyl methacrylate) in the matrix of polyurethane was completed by the opening of a double bond and the formation of a linear polymer in the composition of semi-IPN. Studies of nanocomposites based on multicomponent polymer matrices consisting of polyurethane and poly(hydroxypropyl methacrylate) with 15 and 30 % of the last by FTIR-ATR spectroscopy demonstrated the presence of POSS in the nanocomposites and the influence of POSS content on the structure of the studied systems and on the degree of phase separation. The POSS is "embedded" into the polymer chain between cross-linking of the polyurethane networks, with the additional formation of a complex system of intermolecular hydrogen bonds between the carboxyl and amine components of urethane groups in the nanocomposites.

Recent Advances in Polyurethane/POSS Hybrids for Biomedical Applications

Advanced organic-inorganic materials-composites, nanocomposites, and hybrids with various compositions offer unique properties required for biomedical applications. One of the most promising inorganic (nano)additives are polyhedral oligomeric silsesquioxanes (POSS); their biocompatibility, non-toxicity, and phase separation ability that modifies the material porosity are fundamental properties required in modern biomedical applications. When incorporated, chemically or physically, into polyurethane matrices, they substantially change polymer properties, including mechanical properties, surface characteristics, and bioactivity. Hence, this review is dedicated to POSS-PU composites that have recently been developed for applications in the biomedical field. First, different modes of POSS incorporation into PU structure have been presented, then recent developments of PU/POSS hybrids as bio-active composites for scaffolds, cardiovascular stents, valves, and membranes, as well as in bio-imaging and cancer treatment, have been described. Finally, characterization and methods of modification routes of polyurethane-based materials with silsesquioxanes were presented.

The Effect of POSS Type on the Shape Memory Properties of Epoxy-Based Nanocomposites

Thermally activated shape memory polymers (SMPs) can memorize a temporary shape at low temperature and return to their permanent shape at higher temperature. These materials can be used for light and compact space deployment mechanisms. The control of transition temperature and thermomechanical properties of epoxy-based SMPs can be done using functionalized polyhedral oligomeric silsesquioxane (POSS) additives, which are also known to improve the durability to atomic oxygen in the space environment. In this study, the influence of varying amounts of two types of POSS added to epoxy-based SMPs on the shape memory effect (SME) were studied. The first type contained amine groups, whereas the second type contained epoxide groups. The curing conditions were defined using differential scanning calorimetry and glass transition temperature (T_g) measurements. Thermomechanical and SME properties were characterized using dynamic mechanical analysis. It was found that SMPs containing amine-based POSS show higher T_g, better shape fixity and faster recovery speed, while SMPs containing epoxide-based POSS have higher crosslinking density and show superior thermomechanical properties above T_g. This work demonstrates how the T_g and SME of SMPs can be controlled by the type and amount of POSS in an epoxy-based SMP nanocomposite for future space applications.